1. Field of the Invention
The present invention relates generally to the field of electronic switching apparatus and more particularly to electronic switching apparatus for waveguide switching for microwave applications.
2. Background Discussion
Common to most electrical and electronic apparatus are switching components. These switching components vary from simple mechanical "on-off" switches used to energize equipment to high speed solid state components, such as transistors, used in digital computers.
The most common electronic switches are those used in electrical or electronic circuits, for controlling the flow of electrons. Analogous switches are used in at least some advanced microwave circuits for controlling the flow of microwave energy. As an example, it may be required to switch the microwave output of a transmitter between two separate transmitting antennas. Conversely, it may be required to switch microwave signals received by a common antenna between two or more microwave signal processors. In more complex microwave equipment, it may be necessary to switch microwave signals from two or more sources between two or more pieces of equipment designed to utilize or process such microwave signals. These microwave switches are generally defined with respect to the number of "poles" and "throws" for which the switch is configured.
It should be appreciated that because of the different nature of electrons and microwaves electronic and microwave switches, although both are defined in the same manner, are usually substantially different in construction. In this regard, microwave switches especially those used in waveguide apparatus, are substantially more difficult to implement than are electronic switches, particularly when the microwave switches are required to have low switching losses.
Due to difficulties in providing low-loss microwave switches, especially in the millimeter wavelength range (that is, about 5 gigahertz) microwave waveguide switches typically require inter connections of phase shifters, quadrature hybrids, waveguide terminations, "magic tees" and cross over networks.
Single pole, double throw (SP2T) microwave switches employing the above-mentioned microwave components have been constructed. Single pole four throw (SP4T) microwave switches utilizing a parallel arrangement of two SP2T microwave switches with additional combining networks which have been implemented with such military hardware as the AN/SLQ-17, Threat Reactive Electronic Warfare System presently in use by the United States Navy.
However, as microwave systems increase in complexity and as performance requirements are made more stringent, an important need presently exists for low-loss microwave switches having greater switching capabilities as an example, a need presently exists for a low loss, waveguide SP8T switch, and the potential exists for a DP8T microwave switch, in the millimeter microwave range.
It can, be understood that many types of SPMT microwave switches can be constructed by "treeing" together, in a series-parallel relationship, an appropriate number of microwave switches of lesser switching capacity. In addition a SP8T microwave switch may alternately be constructed by treeing a SP2T switch with two SP4T switches or by treeing a 1-2-4 arrangement of SP2T microwave switches (as further described below).
However, such treeing arrangements of lesser capacity microwave switches in order to construct a greater capacity microwave switch gives rise to an amount of microwave power loss that is excessive for some or many critical microwave applications. These excessive switching losses may, as an example, result in the loss of weak received signals received by an antenna. Moreover such types of composite switches, may require the use of more microwave components and are consequently larger, more costly and possibly less reliable than more specially designed microwave switches. However, to the knowledge of the present inventor no SP8T or 2P8T microwave switches have been developed which do not use simple treeing arrangements of lesser capacity microwave switches and it is to such specifically designed SP8T and SP8T switches that the present invention is described.